The ability to bind epithelial cells is of great importance for several bacterial species. For example, Staphylococcus aureus and Streptococcus pyogenes possess fibronectin binding proteins (FnBP) with related sequence organization. These FnBP are known as Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs). They exploit the modular structure of fibronectin forming extended tandem beta-zippers in its binding to fibronectin. [27, 39, 47, 73] The function is to mediate bacterial adhesion and invasion of host cells.
The important mucosal pathogen Moraxella catarrhalis is the third leading bacterial cause of acute otitis media in children after Streptococcus pneumoniae and Haemophilus influenzae. [14, 40, 55] M. catarrhalis is also one of the most common inhabitants of the pharynx of healthy children.
Furthermore, M. catarrhalis is also a common cause of sinusitis and lower respiratory tract infections in adults with chronic obstructive pulmonary disease (COPD). [74] The success of this species in patients with COPD is probably related in part to its large repertoire of adhesins.
Recent years focus of research has been on the outer membrane proteins and their interactions with the human host. [6, 48, 56] Some of these outer membrane proteins appear to have adhesive functions including amongst others, M. catarrhalis IgD binding protein (MID, also designated Hag), protein CD, M. catarrhalis adherence protein (McaP) and the ubiquitous surface proteins (Usp). [1, 22, 33, 48, 61, 81, 84]